1. Field of the Invention
The invention relates to coatings on a sol-gel basis, formed from silane-functional oxalamides which have been hydrophilicized by way of alkoxyalkyl radicals.
2. Description of the Prior Art
Sol-gel condensates are frequently employed for coatings. They are prepared by mixing suitable compounds of low molecular mass with crosslinkable groups in a solvent, then adding water and catalysts if desired to initiate the hydrolysis and/or condensation reaction. The conduct of such sol-gel operations is known in principle to the skilled worker and described for example in Journal of Non-Crystalline Solids 48 (1982) 11-16. A drawback of the prior art systems, however, is that in general it is necessary to add organic solvents, since the low molecular mass compounds used are not, or not fully, miscible with water. Frequently, however, for many applications, the use of organic solvents is specifically unwanted.
An object which therefore existed was that of finding water-soluble compounds which react by hydrolysis and condensation to form crosslinked sol-gel materials and can be used to coat substrates.
Oxalamides of the general formula (I)(R1O)3-nR2nSi—CH2—CH2—CH2—NH—CO—CO—HN—CH2—CH2—CH2—Si(OR1)3-nR2n  (I)are known in principle. EP-A 729 963 and CA-A 2 087 227 describe them as polymer additives and antioxidants, but without giving any indications whatsoever of their possible use for producing water-based sol-gel coatings.